The invention relates to a combined centering and clamping device actuatable by a pressure medium. In assembling automobiles, sheet-metal parts often have to be welded to body sections. To accomplish this, it is desirable to utilize toggle lever clamping devices that will, for instance, reach through openings in the body parts and firmly clamp the parts and center them in the predetermined position until they are fixed in that position. The parts are then joined together by spot welds or the like.
Toggle lever clamp devices are known in the prior art. One such device is the subject of German Patent No. DE 39 36 396 C1 that discloses a toggle lever clamping device that is actuatable by a pressure medium. The device disclosed in this German patent is intended for use especially for auto body parts, and comprises a single or multi-part housing with a cylinder chamber for the piston and a motion chamber for the piston rod and the toggle lever joint assembly. The device also includes a piston rod guide means on the free end of the piston rod which is disposed in the housing and on a piston rod bolt. The device also includes a tab which is pivotally supported on the piston rod bolt and on a toggle lever joint shaft, and a two-armed lever whose drive end is also supported on the toggle lever joint shaft. The two-armed lever forms a rocker that comprises a bell crank, the apex of which is pivotally supported in the housing, and the power takeoff end is coupled to a clamping member through a pivot shaft. A single-armed rocker, of the same length as the lever arm on the power takeoff side of the two-armed rocker, is pivotally supported in the housing (pivot shaft) and extends parallel to the lever arm of the bell crank on the power takeoff side and is coupled to the clamping member through a pivot shaft. When in the clamping position, the pivot shafts are structurally connected to the housing and the toggle lever joint shaft are located on an imaginary straight line on the drive-side end of the bell crank. The imaginary line extends parallel to the longitudinal axis of the piston rod.
This clamping device is embodied as an undercarriage clamp whose clamping member on the clamping end has a clamping hook that reaches through an opening in the bearing face of the workpiece and whose clamping face is oriented toward the clamping device. A centering mandrel, forming a hollow chamber secured to the housing, is provided which encloses the clamping hook in the unclamped position and allows it to protrude radially in the clamping position.
Another toggle lever clamping device that is actuatable by a pressure medium, and is intended especially for auto body parts, is disclosed in German Patent Disclosure DE 39 38 208. This device comprises a single or multi-part housing with a cylinder chamber for the piston, and a motion chamber for the piston rod and the toggle lever joint assembly. Guide means for the piston rod are provided on the free end of the piston rod, which are guided in guide grooves formed in the housing and in a piston rod bolt. The device includes a tab which is pivotably supported on the piston rod bolt and on a toggle lever joint shaft. There is also a two-armed lever, the drive end of which is supported on the toggle lever joint shaft and its free end acts as a clamping part (clamping hook). There is a pivot bolt braced on the housing and engaging the clamping lever wherein the pivot bolt is guided in a slot of the housing, and a rocker that is pivotally supported in the housing is also supported on the toggle lever joint axis by its other rocker end.
The device includes a pivot bolt that has at least one roller that guides the pivot bolt in a slot that intersects with the longitudinal axis of the piston rod at an acute angle. The device also includes a tab on the toggle lever joint assembly that is pivotally joined to a rocker about a shaft structurally connected to the housing through a toggle lever joint axis extending immovably parallel to the piston rod bolt. The longitudinal pivot axis extends parallel to the piston rod bolt and to the toggle lever joint axis.